1 //=== BuiltinFunctionChecker.cpp --------------------------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This checker evaluates clang builtin functions. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "ClangSACheckers.h" 15 #include "clang/Basic/Builtins.h" 16 #include "clang/StaticAnalyzer/Core/Checker.h" 17 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 19 20 using namespace clang; 21 using namespace ento; 22 23 namespace { 24 25 class BuiltinFunctionChecker : public Checker<eval::Call> { 26 public: 27 bool evalCall(const CallExpr *CE, CheckerContext &C) const; 28 }; 29 30 } 31 32 bool BuiltinFunctionChecker::evalCall(const CallExpr *CE, 33 CheckerContext &C) const { 34 ProgramStateRef state = C.getState(); 35 const FunctionDecl *FD = C.getCalleeDecl(CE); 36 const LocationContext *LCtx = C.getLocationContext(); 37 if (!FD) 38 return false; 39 40 switch (FD->getBuiltinID()) { 41 default: 42 return false; 43 44 case Builtin::BI__builtin_unpredictable: 45 case Builtin::BI__builtin_expect: 46 case Builtin::BI__builtin_assume_aligned: 47 case Builtin::BI__builtin_addressof: { 48 // For __builtin_unpredictable, __builtin_expect, and 49 // __builtin_assume_aligned, just return the value of the subexpression. 50 // __builtin_addressof is going from a reference to a pointer, but those 51 // are represented the same way in the analyzer. 52 assert (CE->arg_begin() != CE->arg_end()); 53 SVal X = state->getSVal(*(CE->arg_begin()), LCtx); 54 C.addTransition(state->BindExpr(CE, LCtx, X)); 55 return true; 56 } 57 58 case Builtin::BI__builtin_alloca: { 59 // FIXME: Refactor into StoreManager itself? 60 MemRegionManager& RM = C.getStoreManager().getRegionManager(); 61 const AllocaRegion* R = 62 RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext()); 63 64 // Set the extent of the region in bytes. This enables us to use the 65 // SVal of the argument directly. If we save the extent in bits, we 66 // cannot represent values like symbol*8. 67 DefinedOrUnknownSVal Size = 68 state->getSVal(*(CE->arg_begin()), LCtx).castAs<DefinedOrUnknownSVal>(); 69 70 SValBuilder& svalBuilder = C.getSValBuilder(); 71 DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder); 72 DefinedOrUnknownSVal extentMatchesSizeArg = 73 svalBuilder.evalEQ(state, Extent, Size); 74 state = state->assume(extentMatchesSizeArg, true); 75 assert(state && "The region should not have any previous constraints"); 76 77 C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R))); 78 return true; 79 } 80 81 case Builtin::BI__builtin_object_size: { 82 // This must be resolvable at compile time, so we defer to the constant 83 // evaluator for a value. 84 SVal V = UnknownVal(); 85 llvm::APSInt Result; 86 if (CE->EvaluateAsInt(Result, C.getASTContext(), Expr::SE_NoSideEffects)) { 87 // Make sure the result has the correct type. 88 SValBuilder &SVB = C.getSValBuilder(); 89 BasicValueFactory &BVF = SVB.getBasicValueFactory(); 90 BVF.getAPSIntType(CE->getType()).apply(Result); 91 V = SVB.makeIntVal(Result); 92 } 93 94 C.addTransition(state->BindExpr(CE, LCtx, V)); 95 return true; 96 } 97 } 98 } 99 100 void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) { 101 mgr.registerChecker<BuiltinFunctionChecker>(); 102 } 103
